1 /* 2 * Copyright (c) 2012, 2013, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 package java.util.function; 26 27 /** 28 * Represents an operation on a single operand that produces a result of the 29 * same type as its operand. This is a specialization of {@code Function} for 30 * the case where the operand and result are of the same type. 31 * 32 * <p>This is a <a href="package-summary.html">functional interface</a> 33 * whose functional method is {@link #apply(Object)}. 34 * 35 * @param <T> the type of the operand and result of the operator 36 * 37 * @see Function 38 * @since 1.8 39 */ 40 @FunctionalInterface 41 public interface UnaryOperator<T> extends Function<T, T> { 42 43 /** 44 * Returns a unary operator that always returns its input argument. 45 * 46 * @param <T> the type of the input and output of the operator 47 * @return a unary operator that always returns its input argument 48 */ identity()49 static <T> UnaryOperator<T> identity() { 50 return t -> t; 51 } 52 } 53